A technical question about the DFV

Hi all,I'm making researches about the first version of the FORD Cosworth DFV and I noticed an electric device that disappeared from 1968 onwards, here it is pointed with the red arrow:With the blue arrows I pointed the 2 wires (in a single black insulation) exiting from the device and going towards the LUCAS OPUS system (judging by other 1967 Lotus 49 pictures) via a thin metal tube running over the righthand cam cover.Does anybody know what was the purpose of this little box?Many thanks in advance!Best,Gab

Likely some sort of crank sensor for ignition timing. A 4-stroke engine controller needs two timing inputs, one for determining crank angle and one for determining which phase of the cycle it's on (ie. compression stroke vs exhaust stroke).

Powersteer,the thin metal tube is on the LEFT of the picture but I use to call "right" that side of the DFV because it WAS the right side of the engine.

Well the point I was trying to make was....do you think it run around the intake from one side to the other, crank to camshaft? Maybe its a sensor from the crank to cam to see how much cam the belt driven cam was giving away from belt flexing.

Never having worked on the king of cam drives I'll take your word for it, but certainly torsional deflection of the camshaft itself has given various people grief over the years. And just thinking about it, what about Delrin (???the brown resin impregnated cloth) gears and the like?

The DFV ran a flexible drive in its' compound gear - it's often referred to as the "Keith Duckworth Compliant Gear". I don't have one to hand but essentially the two gears are coupled together via a series of pins that allow for a small amount of deflection in an effort to decouple the torsional vibration of the bottom end from the stab torques of the valves. The down side of this is that your cam timing is compromised as you have to back it off enough to take the flex into account. The whole system must be very carefully looked after and regularly crack tested.

Although the Ilmor 265A is erroneously refereed to as being similar to the DFX (the Indy version of the DFV) one of the major differences was the absence of the compliant drive. This was probably the biggest issue with the engine and nearly killed the whole program. In the end Mario Illen came up with two pendulum mass dampers on the geartrain that solved the problem without compromising the cam timing.

[quote name='Patrick Morgan' date='Feb 26 2013, 23:43' post='6142786']
The DFV ran a flexible drive in its' compound gear - it's often referred to as the "Keith Duckworth Compliant Gear". I don't have one to hand but essentially the two gears are coupled together via a series of pins that allow for a small amount of deflection in an effort to decouple the torsional vibration of the bottom end from the stab torques of the valves. The down side of this is that your cam timing is compromised as you have to back it off enough to take the flex into account. The whole system must be very carefully looked after and regularly crack tested.

Now I am not sure if this is not just another obscure joke - your fault GG.

Tony, there is no end to your treasure trove. Thanks, that's the item. It's a very cleaver solution. That's what's so neat about restoring older stuff, you get to see lots of different solutions to the same problem.

I asked one of my guys about the sensor this morning. He built DFV's in the late 1970's / early 1980's. It seems to be the crank trigger but of a much earlier style than what he was used to. Neather of us could work out what it triggered off?? Possibly the trigger disc is missing in the photo. It is certainly a very early photograph - the fuel pump is mounted on the engine (although curiously the bevel drive for the cable seems to be present as well) and the ignition unit looks to have a fabricated cover. The trumpets are certainly very early.

I asked one of my guys about the sensor this morning. He built DFV's in the late 1970's / early 1980's. It seems to be the crank trigger but of a much earlier style than what he was used to. Neather of us could work out what it triggered off?? Possibly the trigger disc is missing in the photo. It is certainly a very early photograph - the fuel pump is mounted on the engine (although curiously the bevel drive for the cable seems to be present as well) and the ignition unit looks to have a fabricated cover. The trumpets are certainly very early.

Hope that helps.

In numerous sources, reference is made to a "40-tooth reluctor wheel attached to the front of the crankshaft," which obviously is not installed in this photo.

I have to say in defence of my apparent stupidity that I have never heard of another similar racing engine to the DFV that had a similar "compliant" gear. If the DFV is the only one - why did it need such a thing?

Oddly enough I think I have seen a vaguely similar arrangement on a road-going Toyota (I think it was a Toyota) twin-cam engine. In this engine the second camshaft was driven from the first camshaft by a split, spring-loaded gear - presumably to overcome rattling/chattering noises from the "stab torques".

I have to say in defence of my apparent stupidity that I have never heard of another similar racing engine to the DFV that had a similar "compliant" gear. If the DFV is the only one - why did it need such a thing?

Oddly enough I think I have seen a vaguely similar arrangement on a road-going Toyota (I think it was a Toyota) twin-cam engine. In this engine the second camshaft was driven from the first camshaft by a split, spring-loaded gear - presumably to overcome rattling/chattering noises from the "stab torques".

You are not being stupid at all - the DFV was, as far as I know, the first engine to have such a thing hence it was called the "Keith Duckworth compliant gear". Balance and torsional vibration is an extremely complex subject, one I cannot hope to ever understand properly. Different people do different things. Some of the F1 V8 engine for example seem to couple the two cams together both at the front and the back to more the "nodes" and reduce cam twist. If you look at photos of the BMW engine from 2008 for example that had lumps both front and back of the cam cover. Some aero engines (the Write Cyclone is the first that comes to mind) had a mass damper that floated on the crank web. I dread to think how heavy that is!

The Judd EV engine from 1990 has the same compliant gear arrangement as the DFV on the pump drives albeit much smaller. In an ideal world you would try to get away for anything twisting if you can and the mass damper is not a bad way to do it but it does add inertia to the system.

Oddly enough I think I have seen a vaguely similar arrangement on a road-going Toyota (I think it was a Toyota) twin-cam engine. In this engine the second camshaft was driven from the first camshaft by a split, spring-loaded gear - presumably to overcome rattling/chattering noises from the "stab torques".

Very common on production DOHC V6/V8, particularly Japanese. Chain pretensioner, sort of.

You are not being stupid at all - the DFV was, as far as I know, the first engine to have such a thing hence it was called the "Keith Duckworth compliant gear". Balance and torsional vibration is an extremely complex subject, one I cannot hope to ever understand properly. Different people do different things. Some of the F1 V8 engine for example seem to couple the two cams together both at the front and the back to more the "nodes" and reduce cam twist. If you look at photos of the BMW engine from 2008 for example that had lumps both front and back of the cam cover. Some aero engines (the Write Cyclone is the first that comes to mind) had a mass damper that floated on the crank web. I dread to think how heavy that is!

The Judd EV engine from 1990 has the same compliant gear arrangement as the DFV on the pump drives albeit much smaller. In an ideal world you would try to get away for anything twisting if you can and the mass damper is not a bad way to do it but it does add inertia to the system.

The big aircraft radials used a depleted uranium mass. There was quite an assortment of cam dampers on the IRL V8s. As you said earlier, "That's what's so neat about restoring older stuff, you get to see lots of different solutions to the same problem." That's it exactly. The most fascinating stuff in the world.

And while I'm at it, a detail from my cutaway of the DFX showing the "Keith Duckworth Compliant Gear" and a bare crankshaft nose. Either a different system was in use, or I missed it and no-one complained at the time.

Oddly enough I think I have seen a vaguely similar arrangement on a road-going Toyota (I think it was a Toyota) twin-cam engine. In this engine the second camshaft was driven from the first camshaft by a split, spring-loaded gear - presumably to overcome rattling/chattering noises from the "stab torques".

Oddly enough I think I have seen a vaguely similar arrangement on a road-going Toyota (I think it was a Toyota) twin-cam engine. In this engine the second camshaft was driven from the first camshaft by a split, spring-loaded gear - presumably to overcome rattling/chattering noises from the "stab torques".

Eliminates backlash by maintaing pressure on both leading and trailing faces of the gears. Problems arising from backlash include NVH and resonances and accelerated wear.

Some aero engines (the Write Cyclone is the first that comes to mind) had a mass damper that floated on the crank web. I dread to think how heavy that is!

Fairly common - a device to damp crankshaft torsional vibrations. The DFV device is much less common in damping the drive between two seperate shafts. Napier had to put something like that between the two (geared) crankshafts of the H-24 Sabre.

It is interesting to see the extent of Torsional Vibration Damping in current F1 Engines. I understand the Cosworth CA has 7 TVD systems. The large base diameter hollow camshafts are driven by an internal quill shaft. No doubt sized to manage the excitation frequency's involved.

I was under the [misguided?] impression that they all used some form of pneumatic or solenoid driven valves

Pneumatically closed, but opened via camshafts. How long that will remain we shall see. Charles is right, there was a time when new technology was trumpeted, now you can't find out much more than rumour and conjecture. Conjecture - today's special word.

The Ferrari 049 engine had TVBs on the camshafts, at the rear of the engine, with the geartrain at the front. I wasn't allowed to see them.

The big aircraft radials used a depleted uranium mass. There was quite an assortment of cam dampers on the IRL V8s. As you said earlier, "That's what's so neat about restoring older stuff, you get to see lots of different solutions to the same problem." That's it exactly. The most fascinating stuff in the world.

Depleted Uranium? In the '30s and '40s?

Pratt & Whitney's R-2800 went through a lot of development with regards to TVs. The A and B series engines had tungsten weights bolted to the crank counterweights, with a pair of floating "hockey puck" dampers on one. They were also tungsten.

Later R-2800s used basically floating counterweights on front and rear counterweights. One was tuned to damp 2nd order vibrations, the other 4.5 order vibration.

Fairly common - a device to damp crankshaft torsional vibrations. The DFV device is much less common in damping the drive between two seperate shafts. Napier had to put something like that between the two (geared) crankshafts of the H-24 Sabre.

Aero engines often used torsionally flexible shafts to connect things together. Not sure if there were any between the Sabre's cranks and the reduction gear.

Each crankshaft drove two gears through straight cut spur gears. Those were attached to helically cut gears which drove the main reduction gear. These gears were mounted on a sprung balance beam. I can't quite see how the sleeve drive shafts are driven, but it looks to be from one of the first stage reduction gears on each side.

The supercharger was driven by torsionally flexible shafts which ran from the reduction gear through the sleeve drive shaft to the supercharger gears.

The Allison V-1710 had a TV damper at the rear of the crankshaft. The Rolls-Royce Merlin did not - it relied on torsionally flexible shafts. The clutches in the supercharger drive also had some slip allowed.

Both the Allison and Merlin had the cam drives off the rear of the engine. The Griffon had all accesories driven off the front (with the reduction gear) as well as the came drive. Originally the supercharger drive was taken from the front, but later versions had that coming off the rear. I think drive was taken from the front to remove as much variation between crank and cams as they could.